At the moment, there's no way to run a test end-to-end through Android Pay. In test mode, when you generate a test token, Google will always send back the fake token with the id set as TEST_GATEWAY_TOKEN. This is not a valid token id and you can't send it to your server to charge it.

If you get that id, it usually means that your application is configured properly. In that case, what Stripe recommends is to then create a separate token through the API for one of Stripe's test card and then let your server charge that specific token to pretend you went through the flow end-to-end.

From what I've heard, this is something that Stripe and Google are working on improving so that Test mode works properly in the future but no firm timeline.